如何将通过 ctype malloc 分配的二进制缓冲区保存到 Python 中的文件？

发布于 2024-12-11 01:48:54 字数 340 浏览 0 评论 0原文

我有以下代码

import ctypes
pBuf = ctypes.cdll.msvcrt.malloc(nBufSize)
# wrote something into the buffer

如何使用 Python 2.5 将缓冲区的内容保存到文件中？

您可能已经知道，这是行不通的，给出 TypeError: argument 1 must be string or read-only buffer, not int：

f = open("out.data","wb"
f.write(pBuf)

原文

I have the following code

import ctypes
pBuf = ctypes.cdll.msvcrt.malloc(nBufSize)
# wrote something into the buffer

How do I save the content of the buffer to a file using Python 2.5?

As you may already know, this is not going to work, giving TypeError: argument 1 must be string or read-only buffer, not int:

f = open("out.data","wb"
f.write(pBuf)

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旧竹 2024-12-18 01:48:54

也许最好用 ctypes.create_string_buffer()< 分配缓冲区/code>而不是 malloc()。在这种情况下，您可以通过 buf.raw 访问数据。

如果您需要访问 malloc()ed 数据，可以使用 ctypes.string_at(address, size), mybe 与转换为 ctypes.c_void_p 或ctypes.c_char_p，取决于您对内存执行的其他操作以及其中包含的内容（\0 终止的字符串或已知长度的数据）。

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秋凉 2024-12-18 01:48:54

将缓冲区转换为指向字节数组的指针，然后从中获取值。另外，如果您使用的是 64 位系统，则需要确保将 malloc 的返回类型设置为 c_void_p（不是默认的 >int)，这样返回值就不会丢失任何位。

您还需要小心，以防数据中嵌入了 NUL - 您不能只将指针转换为 c_char_p 并将其转换为字符串（如果是这样，则尤其如此）你的数据根本不是以 NUL 结尾的）。

malloc = ctypes.dll.msvcrt.malloc
malloc.restype = ctypes.c_void_p

pBuf = malloc(nBufSize)
...
# Convert void pointer to byte array pointer, then convert that to a string. 
# This works even if there are embedded NULs in the string.
data = ctypes.cast(pBuf, ctypes.POINTER(ctypes.c_ubyte * nBufSize))
byteData = ''.join(map(chr, data.contents))

with open(filename, mode='wb') as f:
    f.write(byteData)

Cast the buffer into a pointer to a byte array, and then get the value from that. Also, if you're on a 64-bit system, you'll need to make sure to set the return type of malloc to a c_void_p (not the default int) so that the return value doesn't lose any bits.

You'll also need to be careful, in case there are embedded NULs in your data -- you can't just convert the pointer into a c_char_p and convert that into a string (which is especially true if your data isn't NUL-terminated at all).

malloc = ctypes.dll.msvcrt.malloc
malloc.restype = ctypes.c_void_p

pBuf = malloc(nBufSize)
...
# Convert void pointer to byte array pointer, then convert that to a string. 
# This works even if there are embedded NULs in the string.
data = ctypes.cast(pBuf, ctypes.POINTER(ctypes.c_ubyte * nBufSize))
byteData = ''.join(map(chr, data.contents))

with open(filename, mode='wb') as f:
    f.write(byteData)

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